An RF junction circulator, duplexer, or T/R switch (or, as will be used in the discussion that follows, a “circulator”) is a three-port device formed by a symmetrical Y junction coupled to magnetically biased ferrite material. Coaxial based components may utilize substrate material for the conductive path of the signal, and the ferrite element to divert the fields between ports. The circulator permits the flow of microwave energy in one direction only, e.g. from port 1 to 2, 2 to 3, and 3 to 1. When one of the ports is terminated with a load under a matched configuration, the other two are isolated in the reverse direction. Thus, an isolator is a circulator which has a matched termination, usually integral to the unit, on port 3.
In these devices, port 1 would be considered the “input” port, 2 would be the input or output port, depending on the application or mode, and 3 would be the output port. For example, in a traditional radar configuration, port 1 is connected to a transmitter, port 2 to the antenna, and port 3 to the receive architecture. In operation, the transmit pulse would propagate from port 1 to port 2; the received signal from the antenna would then go from port 2 to port 3.
Unfortunately, port 1 and port 3 are not completely isolated from one another, thus contributing to leakage into port 3. This leakage of the transmit signal results in degradation in performance of the overall system, as the minimum detectable received signal should be above the leakage signal. If leakage between ports 1 and 3 is reduced, however, the attenuated noise would allow for a cleaner signal from port 2 to be observed at port 3. By way of example, it would enhance minimum detectable ranges of signals, or targets, in radar applications. Additionally, such noise reduction can enable higher achievable dynamic ranges in microwave receiver architectures. From a communications perspective, this would allow reception of even weaker signals in devices which both transmit and receive simultaneously.
Known methods of attenuating undesired internal reflections are either only moderately effective, or operate in a less effective digital, post-analog-processing, regime. As a result, there exists a need in the art for improved systems and methods to reduce or eliminate leakage signals and undesirable internal reflections in microwave circulators.